Chicago PT is developing rehabilitation robotics to help clinicians provide more intensive functional retraining of overground walking, post-stroke. Chicago PT's concept is to build devices that work with the clinician rather than replacing the clinician, in order to retain the clinician's skilled manual connection with the patient in all its important aspects: physical, sensory and psychological. The KineAssist device, proposed for further development and testing here, allows clinicians to safely challenge patients to their limits of gait and dynamic balance, which otherwise could not be done due to the risk of falls. Innovations include the incorporation of dynamic balance and challenge into gait training, training in functional contexts overground rather than on a treadmill, the recording of objective measures and progress, integration into conventional practice, and quick setup and transitions to and from sitting. Chicago PT's commercialization plan begins with leading hospitals as part of a research consortium, followed by in-patient rehabilitation facilities, and later outpatient clinics. Chicago PT intends to form a relationship with an industrial partner to provide the necessary infrastructure for broader distribution. In the proposed Phase I period Chicago PT will further develop its KineAssist device, improving on the prototype device in response to feedback from clinicians, and further advancing certain engineering issues. Significant software development is planned for improved allowance of motion of the patient and accessibility to the clinician, and a new force based interface for clinicians and researchers will be developed. Further, we will demonstrate unimpeded motion with the KineAssist during overground functional tasks. The motions of overground gait and balance tasks will be evaluated both with and without the KineAssist, by healthy individuals as well as stroke survivors, to assess the ability of the KineAssist-patient interface to allow key characteristic motions associated with select functional tasks. Specifically, we hypothesize that kinematic trajectories within the KineAssist will be uninterrupted and continuous. We will attempt to identify tasks where kinematic trajectories are altered by the KineAssist. After these aims are achieved, we will be in a position to initiate human subject testing that will investigate the use of the KineAssist during standardized training protocols. In phase II, we plan to investigate overground and functional walking performance under conditions of body-weight support and under novel destabilizing and stabilizing force-field conditions.